Earlier quoted context omitted.
What made vanilla special was the restrictions placed on the world. Everybody packed into Ironforge or Orgrimmar because that's where the auction houses were. You could chat with tons of people or easily join groups to raid dungeons. Physicality in the world was an important part of the experience. You hung out at the gates of a battleground to play in them, so there was usually a crowd to chat with. When BC came alo…
Although I didn't play Vanilla, as I said above. I've experienced this with the end of Wotlk and beginning of Cata. The introduction to group finder and the ability queue from anywhere for anything really ruined that experience. This caused the game's world to feel empty at least for me anyways.
That crowd in the city, coupled with the worse trace options- back when mounts were for higher level players and were very expensive - made the actual quests feel a lot more remote.
Special mention to the griffins/hippogirffs. One of the greatest moments of joy I felt when I got on one the first time and could still look around as it flew.